LTE (Long Term Evolution), which is standardized by the third generation partnership project (3GPP), may be employed in each of frequency division duplex (FDD) and time division duplex (TDD). Because of easiness in frequency configuration and changeability of proportions of radio resources for uplink and downlink, it is envisaged that TDD is employed in many systems in future for the effective utilization of frequency.
In TDD, a link direction (for example, downlink, and uplink) is set for each subframe. More specifically, a plurality of TDD uplink and downlink configurations (or TDD configurations) each indicating the link direction of each subframe in a radio frame are prepared in advance, and one of the TDD configurations is used. For example, a communication business operator selects one TDD configuration from among seven TDD configurations defined in the LTE technology standard, and sets it in a fixed manner. Further, 3GPP is studying a method which dynamically sets an optimal TDD configuration in response to traffic in a cell, aiming at improving throughput of the entire network in future.
On the other hand, in Non-Patent Literature 1, a configuration of a physical random access channel (PRACH) is set for transmitting a random access preamble in a random access procedure. Also, a radio resource used as PRACH is set for each TDD configuration, with respect to each configuration of PRACH. Then, Non-Patent Literature 2 discloses a concern that a random access preamble transmitted by a user equipment (UE) that does not have capability of this dynamic setting (i.e., a legacy UE) is not received by an eNodeB, when the TDD configuration is set dynamically.